To me, it's good to have a disk with the last version of ubuntu in case I need it. So if I download the disk and boot from it, I'll only download it once, versus downloading the iso + downloading the upgrade.

Also, the upgrade to a new version famously have many problems. I just tried it and it crashed in the middle :S

I just boot from disk so I can get the upgrade done as quickly as possible. This way, my machine does everything it needs to upgrade, without anything else going on. Then when its done, I let it update in the background while I make sure everything went smoothly.

In this case, it went very smoothly for me, and was worth the hassle. I upgraded from Ubuntu 11.04, which had been rather a bit of a mess actually, in the Unity/Gnome3/fvwm shell department, as in I had them all and had to switch around to get certain things I liked. Unity crashed too often (in 11.04) for me to trust it.

That has all changed. I am now running Ubuntu studio, which features fvwm, and nothing else. Gnome only if I truly need it, and Unity .. after the dust settles.

So I'm quite comfortable in my upgrade to 12.04, and everything works like it should - full multi-channel digital audio, multi-monitor support with acceleration, and so on.

It will, as soon as the release data percolate through the mirror network and reaches the mirror you are using.

I'm pretty sure in the past that the upgrade software itself was updated, so you have to update the old packages first to make sure the new stuff installs properly.

At any rate, better safe than sorry.